The aim of the study is to evaluate the association between regional cerebral blood flow (rCBF) and anxiety. Regional cerebral blood flow will be measured under resting conditions and during acute anxiety in patients with anxiety disorders and matched normal controls. 133Xenon inhalation technique will be utilized for measurement of the brain capillary perfusion. Degrees of anxiety during the cerebral blood flow measurement will be quantified via rating scales and peripheral physiological indices. Several anxiety related variables such as hematocrit, fibrinogen, hemoglobin and carbon dioxide which have been implicated in the control of cerebral blood flow will be monitored. Anxiety will be induced in both patients and controls via an intravenous infusion of .2 microgram/Kg/mt of epinephrine or normal saline given under double-blind conditions. This project might identify the brain regions related to anxiety. This information will be of considerable value to similar research projects on other psychiatric illnesses since anxiety is a component of most psychiatric conditions. It will also examine the possible use of CBF as an objective index of anxiety. The results of the study may facilitate neurochemistry research on psychiatric disorders. It would also explain the central mechanisms of cerebral ischemia, commonly associated with acute anxiety. Lastly, it might provide new insights into the association between anxiety, mitral valve prolapse and stroke.